41. Cosmological implications

Given the consistency of Hubble constants derived, both locally and at
large recessional velocities, then we can state that
H0 falls
within the full-range extremes of 75 ± 1 and 68 ± 5 km/sec/Mpc,
giving formally H0 = 72 (±
2)r
[± 12]s km/sec/Mpc out to a
velocity-distance 0.1c (30,000 km/sec.) These results are summarized
graphically in Figure 38 and
numerically in Table 5.

A value of the Hubble constant, in combination with an independent
estimate of the average density of the Universe, can be used to
estimate a dynamical age for the Universe (e.g., see
Figure 39).
For a value of of H0 = 72 (±
2)r km/sec/Mpc, the age ranges from
a high of ~ 12 Gyr for a low-density ( = 0.2) Universe, to
a young age of ~ 9 Gyr for a critical-density ( = 1.0) Universe. These ages
change to 15 and 7.5 Gyr, respectively allowing
for a systematic error of ± 10 km/sec/Mpc.

Other, independent constraints on the age of the Universe exist; most
notably, the ages of the oldest stars, as typified by Galactic globular
clusters. These ages traditionally are thought to fall in the range
of 14 ± 2 Gyr
(Chaboyer et al. 1996),
however
the subdwarf parallaxes obtained by the Hipparcos satellite
(Reid 1997)
may reduce these ages considerably. For = 14 Gyr and
= 1.0,
H0 would have to be ~45 km/sec/Mpc. If
constrained by the stellar ages, and interpreted within the context of
the standard Einstein-de Sitter model, our value of H0
= 72 km/sec/Mpc, is incompatible with a high-density ( = 1.0) model
universe without a cosmological constant (at the 2.5-sigma level
defined by the identified systematic errors).